Impulse-controlled printer device

ABSTRACT

There is disclosed a circuit for energizing the solenoid coil of an electromagnet operatively connected to move a type member of a printing mechanism in an electronic data processing machine into a position to print a symbol corresponding to a value registered in the machine. The circuit comprises a diode and a four-layer semiconductor power device connected in series with the solenoid coil and also connected to a source of alternating current. A capacitor is connected in parallel with the coil and the semiconductor device with the discharge time of the capacitor being less than the half-cycle of the alternating current.

United States Patent inventor Appl. No.

Filed Patented Assignee Priority IMPULSE-CONTROLLED PRINTER DEVICE Gunter Schrem Albeck, Germany 763,572

Sept. 30, 1968 Apr. 20, 1971 Walther-Buromaschinen GmbH Gerstetten-Wurttemberg, Germany Sept. 28, 1967 Germany P 15 49 962.4

PHOTOCELL 35, 28, 34 (Cursory) [5 6] References Cited UNITED STATES PATENTS 2,928,896 3/1960 Dirks 178/34 Primary Examiner-Kathleen H. Claffy Assistant Examiner-Thomas W. Brown Attorney-Edmund M. J askiewicz ABSTRACT: There is disclosed a circuit for energizing the solenoid coil of an electromagnet operatively connected to move a type member of a printing mechanism in an electronic data processing machine into a position to print a symbol corresponding to a value registered in the machine. The circuit comprises a diode and a four-layer semiconductor power device connected in series with the solenoid coil and also connected to a-source of alternating current. A capacitor is connected in parallel with the coil and the semiconductor device with the discharge time of the capacitor being less than the half-cycle of the alternating current.

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GUNTER SCHREM ATTORNE llii/lllllULSlE-QONTRGLLED PRINTER DEVICE The present invention relates to an impulse-controlled printer device for calculating machines, electronic data processing machines and the like wherein type carriers are moved to predetermined positions by a mechanism actuated by electromagnets, more particularly, to a circuit for delivering impulses to energize the electromagnets.

in one form of a line printer for data processing machines and the like a number of closely adjacent parallel type wheels may be simultaneously rotated to printing positions corresponding with the values registered in the machine. A perforated sector gear is pivoted to a position in response to a value registered in the machine whereupon an electromagnet is energized to move a stopping pawl to lock in position a toothed sector gear which moves a type wheel into position to print a predetermined digit or symbol. The type wheel is pivoted to this position and then locked therein so that during the printing operation the predetermined symbol or value is printed against a printing roll. By way of example, in order to print the digit 3, the perforated sector gear will be pivoted into a position after three light pulses have passed through the perforations to energize a photoelectric cell which in turn has given three impulses to a counting device. By the release of a control impulse, electric current will be transmitted to the associated electromagnetic to energize the magnet to cause the stopping pawl to engage the third tooth of a ratchet segment on the perforated sector gear. The type wheel associated with this perforated sector gear will be held stationary in the position wherein the digit 3 is positioned for being printed on a paper tape.

The number of type wheels would correspond with the number of digits which could be printed in a line. If ten-digit lines were to be printed, then ten type wheels would be positioned closely adjacent to each other and each type wheel is actuated in response to its respective electromagnet. The type wheel will be stopped in any predetermined position in response to the position into which the stopping pawl is pivoted. The printing of the entire line of digits will then occur simultaneously for all type wheels at the end of the machine travel.

It is readily apparent that because of the high-speed operation of data processing machines, calculating machines and the like it is necessary for the printer devices to operate at corresponding high speeds so as to be able to keep up with the output from the machines. The attraction I of the electromagnetic cores must therefore perform their functions in time periods of the order of one-hundredth of a second. li-Iowever, considerable difficulties have been encountered in controlling such high speed switching operations wherein the operation has such a short duration by the use of relays or other mechanical switching devices. Such switching devices are not only relatively slow acting but also are subject to considerable wear.

It is therefore the principal object of the present invention to provide a novel and improved control mechanism for line printers of the type described herein.

It is another object of the present invention to provide a control mechanism that is operable without the use of mechanical elements for positioning type wheels of a line printer.

It is a further object of the present invention to provide a control mechanism in the form of a circuit employing semiconductor devices for positioning type wheels of a line printer in response to values registered in a data processing machine and the like.

The present invention may be incorporated in an electronic data processing machine, calculating machine and the like having a printer mechanism wherein a type wheel is moved into a position to print a symbol or digit corresponding to a value registered in the machine. The type wheel is operatively connected through a suitable mechanism so as to be actuated by an electromagnet having a solenoid coil. Connected in series with the solenoid coil is a diode and a controlled semiconductor device such as a silicon controlled rectifier or thyristor. The diode and semiconductor device are also connected to a source of alternating current and a capacitor is connected in parallel with the coil and the semiconductor device. The discharge time of the capacitor across the series circuit is less than the half-cycle of the alternating current used for energizing the system.

In order that the linkage system operatively connecting the electromagnet and the stopping pawl operates with sufficient force, a strong pulse of electric current must flow through the solenoid coil when the electromagnet is energized. The semiconductor switch connected in front of the solenoid coil must permit the flow therethrough of a pulse of electric current without sustaining any damage. Further, the semiconductor power switch must be relatively small and inexpensive since a switching device is required for every type wheel of a multiple digit printer mechanism.

The thyristor employed in the present invention is particularly suitable for this purpose. As is known in the art, a silicon controlled rectifier begins ionization when an electric pulse is delivered to the gate electrode, thereby establishing a current flow between the power circuit electrodes. It has been previously considered necessary to employ relatively complicated circuits to switch the silicon controlled rectifier between its two stable states.

The circuit as disclosed herein is simple and reliable and requires a minimum of space. Further the simplicity of this circuit enables a large number of silicon controlled rectifiers to be employed in multiple digit printer devices.

Other objects and advantages of the present invention will be apparent upon reference to the accompanying description when taken in conjunction with the following drawings wherein:

FIG. 1 is a side elevational view of a portion of a printing mechanism operated in accordance with the present invention;

FIG. 2 is a perspective view of the electromagnets together with the associated levers and stopping pawls for positioning the type wheels; and

FIG. 3 is an electrical circuit diagram showing schematically the circuit of the present invention.

Proceeding next to the drawings wherein like reference symbols indicate the same parts throughout the various views a specific embodiment of the present invention will be described in detail.

The printing mechanism disclosed herein is only a portion of the complete printing mechanism which is described in greater detail in the copending US. Pat. Application Ser. No. 647,l23 and filed June 19, 1967, now US. Pat. No. 3,453,953.

As may be seen in FIG. 1, a collecting shaft 1 is moved about the rotational axis of a shaft 4 in the direction of the arrow in a known manner. Pivotally mounted on shaft 4 is a sector gear 3 which is maintained against collecting shaft I by means of a spring 2. The sector gear 3 has gear teeth 30 along a peripheral portion thereof and ratchet teeth 4a along another peripheral portion. An electromagnet 5 having a solenoid coil 50 and a core 5b is energized to attract arm 70 of an actuating lever 7 which is pivotally mounted on a shaft 6. Pivoting of actuating lever 7 in a counterclockwise direction lifts a contact nose 7a to release a tab or bent end 9a on a stopping pawl 9 which is pivotally mounted at 10. The pawl 9 is provided with a pawl hook 9b which is positioned immediately adjacent ratchet teeth 4a of the sector gear 3.

As collecting shaft 1 is moving in the direction of the arrow the sector gear 3 will rotate in a clockwise direction under the action of the spring 2 until energization of electromagnet 5 causes the pawl hook 912 of pawl 9 to engage a selected ratchet tooth corresponding to a digit registered in the machine and to be printed. The sector gear 3 will then be held in this position for printing. This positioning of sector gear 3 will cause gear teeth 3a to rotate intermediate gears 30a and 30b to the position wherein type wheel 300 will present the predetermined digit in a printing position. The mounting and actuation of these intermediate gears and the type wheel are known.

The actual printing operation is accomplished by impacting the type wheel against a printing roller in a known manner. After the printing operation has been completed, collecting shaft 1 is moved back in the direction of the dotted arrow to contact shoulder 4b of sector gear 3 to move the sector gear 3 back to its original position as shown in FIG. I. The inclined surface at the left-hand end of ratchet teeth 4a as seen in FIG. 1 will cam the pawl hook 9b, and accordingly pawl 9 back to its original position. At the same time, a bridge ll which is pivotally mounted on shaft 10 (shown also in H0. 2) will be pivoted under the action of collecting shaft 1 engaging an abutment 11a. This pivoting movement of bridge 1 I will cause its pin 12 to act against a front extension 7b to return actuating lever 7 to its original position in the event this lever has not already been returned to its original position under the action of spring 8.

The actuating levers 7 which may be more clearly seen in FIG. 2 may be coated with a suitable synthetic resin to prevent them from sticking.

ln order to provide a more compact arrangement the electromagnets 5 are arranged in two parallel rows as shown in FIG. 2 with one electromagnet being provided for each type wheel. The energization of an electromagnet will attract its respective a actuating lever 7 which is pivoted on shaft 6. The actuating levers operated by electromagnets in the lower row have downwardly depending arms 7c whereas the actuating levers operated by the electromagnets in the upper row have upwardly extending arms. However, as will be apparent from H6. 2, all of these actuating levers are pivotally mounted on the common shaft 6. The actuating levers are retained in their normal inoperative positions against a stop bar by springs 8.

A perforated sector gear 13 is pivotally mounted on shaft 4 and carries the collecting shaft 1. The sector gear 13 is provided with a series of perforations 130 which are successively aligned with a photoelectric receiver 25. Negative electric impulses are transmitted from photoelectric receiver 25 across a capacitor 14 to transistor 15 as shown in the circuit diagram of FIG. 3. By means of the potential reversal at the transistor 15, a positive impulse is generated which is transmitted in the form of a trigger signal across a capacitor 16 to the gate of a thyristor 17. The thyristor is a four-layer semiconductor power device which exhibits regenerative or latching-type switching action. This semiconductor device is, in effect, a silicon-controlled rectifier which belongs to a family of similar devices known as thyristors.

The gate electrode of the thyristor may receive an electrical impulse at any time during either the negative half-cycle or the positive half-cycle of an alternating voltage (24 volts) applied to terminal 18. During the negative half-cycle, the total current flowing through the solenoid coil 50 and the thyristor 17 will equal the sum of the discharge current from capacitor 22 and the current flow through diode 20 and resistor 21. If the electrical impulse arrives at the gate electrode of the thyristor during the positive half-cycle of the alternating current voltage 18, then the diode 20 will not conduct any current therethrough, and only the discharge current from capacitor 22 will fiow through the coil 50. On the one hand, the capacitance of capacitor 22 should be of such a value that the discharge current will be sufficient to energize coil 5a sufficiently to actuate the armature of the electromagnet and in turn actuate lever 7 and stopping pawl 9. On the other hand, the capacitance of capacitor 22 should be such that depending on the resistance of the coil 50 and the frequency of the alternating current the discharge time of the capacitor 22 will be less than a half-cycle of the alternating current applied to terminal 18. When the discharge time of the capacitor is less than a half-cycle of the alternating current, the thyristor 17 will always become nonconducting during the positive halfcycle of the alternating-current source 18, and consequently no additional switching devices will then be necessary to change the th ristor l7 to a nonconducting state.

Resistor 2 functions to lrmrt the elec rrc current flowing through diode 20. The diode 20 may be a semiconductor rectifier or a junction diode. lt is pointed out that the time interval between the two ionization stages in the thyristor 17 with respect to the actual ionization time is generally very large. It is therefore possible to extend the charging time over this intermediate period so as to keep the charging current very small. This will then necessitate only a small and relatively inexpensive diode 20.

Thus it can be seen that the present invention has provided a control mechanism operable without the use of mechanical elements for actuating a printer device. Further, the printer device is capable of high speed operation for long periods of time with a minimum of maintenance. The use of a semiconductor power switch together with a diode and capacitor enables the solenoid coil to be quickly energized in response to impulses corresponding to the digit to be printed.

it will be understood that this invention is subject to modification in order to adapt it to different uses and conditions and, accordingly, it is desired to comprehend such modification within this invention as may fall within the scope of the appended claims.

lclaim:

1. In an electromagnetically operable printing mechanism of the type in which a solenoid (5a) is energized to position a printing member in a given position corresponding with a value registered in the machine, the improvement which comprises means for energizing said solenoid, including:

A source of alternating-current voltage (18) having a given frequency;

normally nonconductive thyristor means (17) including a pair of power circuit electrodes connected in series with said solenoid, said thyristor means including also a gate electrode;

a diode (20);

circuit means connecting said diode, said solenoid and said thyristor means in series with said voltage source;

a capacitor (22) connected in parallel across the series branch including said thyristor means and said solenoid, said capacitor having a time constant for effecting a discharge time less than one-half of the period of said alternating current voltage source; and

means for supplying a trigger pulse to said gate electrode to render conductive said thyristor means, thereby effecting energization of said solenoid.

2. Apparatus as defined in claim 1, wherein said means for supplying said trigger pulse to said gate electrode includes a transistor l5). 

1. In an electromagnetically operable printing mechanism of the type in which a solenoid (5a) is energized to position a printing member in a given position corresponding with a value registered in the machine, the improvement which comprises means for energizing said solenoid, including: A source of alternating-current voltage (18) having a given frequency; normally nonconductive thyristor means (17) including a pair of power circuit electrodes connected in series with said solenoid, said thyristor means including also a gate electrode; a diode (20); circuit means connecting said diode, said solenoid and said thyristor means in series with said voltage source; a capacitor (22) connected in parallel across the series branch including said thyristor means and said solenoid, said capacitor having a time constant for effecting a discharge time less than one-half of the period of said alternatinG current voltage source; and means for supplying a trigger pulse to said gate electrode to render conductive said thyristor means, thereby effecting energization of said solenoid.
 2. Apparatus as defined in claim 1, wherein said means for supplying said trigger pulse to said gate electrode includes a transistor (15). 